Multi-axial grid or mesh structures with high aspect ratio ribs

Abstract

A multi-axial geogrid possesses a series of interconnected strands or ribs that are arranged along at least two different axes within the plane of the structure. The strands or ribs have an aspect ratio, defined as the ratio of the thickness to width, of greater than 1.0, thickness being the direction normal to the plane of the structure. The geogrid can be manufactured by modifying the process parameters in order to create high aspect ratio ribs, using any of the various known methods for producing geogrids. A reinforced civil engineering structure, and method therefor, is formed by embedding in soil one or more horizontal layers of geogrid having high aspect ratio ribs. The reinforced structure shows improved rutting performance when subjected to vehicular traffic.

What is claimed is: 
     
       1. A multi-axial geogrid comprising a first array of highly oriented ribs extending in a first direction across said geogrid in spaced apart rows and a second array of highly oriented connecting ribs extending in a second direction and interconnecting with adjacent rows of said first array at junctions to form apertures between adjacent oriented ribs extending in the first direction and in the second direction and the junctions between said first and second arrays, said ribs that extend in at least one of the first direction and the second direction having an aspect ratio greater than 1.0 and an aperture stability modulus greater than 0.3 Nm/degree at 20 kg-cm of applied torque. 
     
     
       2. The multi-axial geogrid according to  claim 1 , wherein the geogrid has triangular apertures, and said aspect ratio is between greater than 1.0 and about 2.5. 
     
     
       3. The multi-axial geogrid according to  claim 1 , wherein the geogrid has rectangular apertures, and wherein said aspect ratio is in a range between greater than 1.0 and about 4.0. 
     
     
       4. The multi-axial geogrid according to  claim 1 , wherein the ribs that extend in another of the first direction and the second direction have an aspect ratio greater than 1.0 and an aperture stability modulus greater than 0.3 Nm/degree at 20 kg-cm of applied torque. 
     
     
       5. The multi-axial geogrid according to  claim 1 , wherein said geogrid is embedded in a particulate material so that the particulate material is at least partially interlocked in said apertures. 
     
     
       6. The multi-axial geogrid according to  claim 1 , wherein the first array includes a first series of parallel ribs and said second array includes a second series of parallel ribs, the interconnections of said first and second series of ribs at said junctions being essentially perpendicular to form general rectangular apertures. 
     
     
       7. The multi-axial geogrid according to  claim 1 , wherein the geogrid has three or more series of parallel ribs intersecting each other at junctions such that the angles of the intersecting ribs at the junction are angles not equal to 90°. 
     
     
       8. The multi-axial geogrid according to  claim 7 , wherein the geogrid has three series of parallel ribs intersecting each other at the junctions at angles of about 60° to form generally equilateral triangular apertures. 
     
     
       9. The multi-axial geogrid according to  claim 1 , wherein the ribs have a concave cross-section at or near a center thereof. 
     
     
       10. The multi-axial geogrid according to  claim 1 , wherein a material composition of the ribs in the first array is the same as a material composition of the ribs in the second array. 
     
     
       11. A civil engineering reinforcing structure, comprising a multi-axial geogrid including an array of molecularly oriented ribs extending across said geogrid in spaced apart rows in a first direction and an array of molecularly oriented connecting ribs extending in a second direction and joined at interconnecting junctions with adjacent rows of said ribs extending in said first direction to form apertures between adjacent molecularly oriented ribs in said first direction and in said second direction as joined at said interconnecting junctions, said molecularly oriented ribs in at least one of the first direction and the second direction having an aspect ratio greater than 1.0 and an aperture stability modulus greater than 0.3 Nm/degree at 20 kg-cm of applied torque in the completed geogrid constituting the civil engineering reinforcing structure. 
     
     
       12. The civil engineering reinforcing structure according to  claim 11 , wherein said geogrid is embedded in a particulate material so that the particulate material is at least partially interlocked in said apertures. 
     
     
       13. The civil engineering reinforcing structure according to  claim 11 , wherein said geogrid is formed by biaxially stretching a general flat polymer starting sheet having a plurality of spaced holes therein. 
     
     
       14. The civil engineering reinforcing structure according to  claim 11 , wherein the ribs in the array extending in the first direction are essentially perpendicular to the ribs in the array extending in the second direction to form generally rectangular apertures or openings. 
     
     
       15. The civil engineering reinforcing structure according to  claim 14 , wherein the aspect ratio is in a range between greater than 1.0 and about 4.0. 
     
     
       16. The civil engineering reinforcing structure according to  claim 11 , wherein the geogrid has a third array of oriented ribs intersecting each other at junctions such that the angles of the intersecting ribs of the three arrays at the junctions are angles not equal to 90°. 
     
     
       17. The civil engineering reinforcing structure according to  claim 16 , wherein the angles of the intersecting ribs are about 60° to form generally equilateral triangular apertures. 
     
     
       18. The civil engineering reinforcing structure according to  claim 11 , wherein the geogrid has triangular apertures, and wherein said aspect ratio is between greater than 1.0 and about 2.5. 
     
     
       19. The civil engineering reinforcing structure according to  claim 11 , wherein the ribs have a concave cross-section at or near a center thereof. 
     
     
       20. The civil engineering reinforcing structure according to  claim 11 , wherein said molecularly oriented ribs in the second direction have an aspect ratio which is greater than 1.0. 
     
     
       21. The civil engineering reinforcing structure according to  claim 11 , wherein a material composition of the ribs in the first array of the completed geogrid is the same as a material composition of the ribs in the second array of the completed geogrid. 
     
     
       22. The multi-axial geogrid according to  claim 1 , wherein the aperture stability modulus is greater than 0.45 Nm/degree at 20 kg-cm of applied torque. 
     
     
       23. The multi-axial geogrid according to  claim 4 , wherein the aperture stability modulus is greater than 0.45 Nm/degree at 20 kg-cm of applied torque.